Acidithiobacillus sp. applied to sewage sludge bioleaching: perspectives for process optimization through the establishment of optimal operational parameters.

Using Acidithiobacillus sp. during bioleaching assays is a well-known biological approach to solubilizing metals within sewage sludge. However, sludge dewatering has also been reported as a secondary treatment benefit. Based on a literature review, the present work provides perspectives regarding the enhancement of bioleaching outcomes on a laboratory scale by establishing optimal operational parameters. Data from different studies suggest that greater bioleaching efficiency may be achieved using a 10% (v/v) mixed inoculum of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans in a ratio of 4:1, supplemented with ferrous sulfate (FeSO4) and elemental sulfur (S0), and an initial system pH near 6.0. However, operational parameters must be established according to the type of sludge being treated due to differences in their compositions. Bioleaching duration is also an aspect that must be considered since treatments conducted for longer than 48 h increased the concentration of Extracellular Polymeric Substances (EPS), a characteristic associated with reducing dewaterability performance.

Extremophilic taxa predominate in a microbial community of photovoltaic panels in a tropical region.

Photovoltaic panels can be colonized by a highly diverse microbial diversity, despite life-threatening conditions. Although they are distributed worldwide, the microorganisms living on their surfaces have never been profiled in tropical regions using 16S rRNA high-throughput sequencing and PICRUst metagenome prediction of functional content. In this work, we investigated photovoltaic panels from two cities in southeast Brazil, Sorocaba and Itatiba, using these bioinformatics approach. Results showed that, despite significant differences in microbial diversity (p < 0.001), the taxonomic profile was very similar for both photovoltaic panels, dominated mainly by Proteobacteria, Bacteroidota and lower amounts of Cyanobacteria phyla. A predominance of Hymenobacter and Methylobacterium-Methylorubrum was observed at the genus level. We identified a microbial common core composed of Hymenobacter, Deinococcus, Sphingomonas, Methylobacterium-Methylorubrum, Craurococcus-Caldovatus, Massilia, Noviherbaspirillum and 1174-901-12 sharing genera. Predicted metabolisms focused on specific genes associated to radiation and desiccation resistance and pigments, were detected in members of the common core and among the most abundant genera. Our results suggested that taxonomic and functional profiles investigated were consistent with the harsh environment that photovoltaic panels represent. Moreover, the presence of stress genes in the predicted functional content was a preliminary evidence that microbes living there are a possibly source of metabolites with biotechnological interest.

Microbiome taxonomic and functional profiles of two domestic sewage treatment systems.

Anaerobic systems for domestic sewage treatment, like septic tanks and anaerobic filters, are used in developing countries due to favorable economic and functional features. The anaerobic filter is used for the treatment of the septic tank effluent, to improve the COD removal efficiency of the system. The microbial composition and diversity of the microbiome from two wastewater treatment systems (factory and rural school) were compared through 16S rRNA gene sequencing using MiSeq 2 × 250 bp Illumina sequencing platform. Additionally, 16S rRNA data were used to predict the functional profile of the microbial communities using PICRUSt2. Results indicated that hydrogenotrophic methanogens, like Methanobacterium, were found in higher abundance in both systems compared to acetotrophic methanogens belonging to Methanosaeta genus. Also, important syntrophic microorganisms (Smithella, Syntrophus, Syntrophobacter) were found in the factory and rural school wastewater treatment systems. Microbial communities were also compared between stages (septic tank and anaerobic filter) of each wastewater treatment stage, revealing that, in the case of the rural school, both microbial communities were quite similar most likely due to hydraulic short-circuit issues. Meanwhile, in the factory, microbial communities from the septic tank and anaerobic filter were different. The school system showed lower COD removal rates (2-30%), which were probably related to a higher abundance of Firmicutes members in addition to the hydraulic short-circuit and low abundance of Chloroflexi members. On the other hand, the fiberglass factory presented higher COD removal rates (60-83%), harboring phyla reported as the core microbiome of anaerobic digesters (Bacteroidetes, Chloroflexi, and Proteobacteria phyla). The knowledge of the structure and composition of wastewater treatment systems may provide support for the improvement of the pollutant removal in anaerobic process.

Cellulolytic and lipolytic fungi isolated from soil and leaf litter samples from the Cerrado (Brazilian Savanna) / Hongos celulolíticos y lipolíticos aislados a partir de muestras de suelo y de hojarasca del Cerrado (Sabana brasileña)

Abstract The Brazilian savanna, known as the Cerrado, is a biome with a high degree of endemism, with the potential to house many microorganisms suitable for biotechnological exploitation, especially fungi. The Cerrado soil, which is usually acidic, is a favorable environment for the growth of fungi capable of degrading lignocellulosic materials. The aim of the present study was to isolate cellulolytic filamentous fungi native to the Cerrado. Samples of soil and leaf litter were collected in three points of Cerrado State Park, located in the South of Brazil, during the rainy season in September 2014. Samples were stored in sterile plastic bags, transported at room temperature and kept at 4 ºC for three days. Filamentous fungi were isolated by successive inoculations in PDA (maintained at 30 ºC). Cellulase activity was tested in CMC (carboxymethyl cellulose) medium and lipase activity was assessed in medium containing phenol red and tween 20 (incubated at 37 °C), and in medium supplemented with Rhodamine B (kept at 30 °C). We isolated a total of 28 strains, 25 produced cellulase, detected with lugol in strains grown in CMC medium. The isolates were identified morphologically (color, form of growth) and by sequencing of the 18S rRNA region, with both techniques producing congruent results. One strain of Colletotrichum boninense and one strain of Trichoderma sp., both isolated from soil samples, presented the highest cellulolytic activity. All strains exhibited lipolytic activity, with enzyme production and activity influenced by temperature. The present study revealed new strains of known filamentous fungi that can be applied in biomass degradation. These strains are suitable for optimization of culture conditions, which could lead to the economic feasibility of the process. Rev. Biol. Trop. 66(1): 237-245. Epub 2018 March 01.

Resumen La sabana brasileña conocida como Cerrado, es un bioma con alto grado de endemismo con el potencial de albergar muchos microorganismos de alto interés biotecnológico. Los hongos producen muchas enzimas que se aplican ampliamente en procesos industriales. El suelo del Cerrado, que suele ser ácido, es un ambiente favorable para el crecimiento de hongos capaces de degradar materiales lignocelulósicos. El objetivo del presente estudio fue aislar los hongos celulolíticos filamentosos nativos del Cerrado. Muestras de suelo y de hojarasca fueron recolectadas en el Parque Estatal del Cerrado, ubicado en el sur de Brasil. De 28 cepas aisladas, 25 produjeron celulasa que fue detectada con lugol. Las cepas fueron cultivadas en medio CMC (carboximetilcelulosa). Los aislados fueron identificados morfológicamente (color, forma de crecimiento) y por secuenciación de la región 18S rRNA, produciendo resultados congruentes. Una cepa de Colletotrichum boninense y una cepa de Trichoderma sp., ambas aisladas de muestras de suelo, presentaron la mayor actividad celulolítica. Todas las cepas mostraron actividad lipolítica, la producción y la actividad se vieron influidos por la temperatura. El presente estudio revela nuevas cepas de hongos filamentosos conocidos con potencial de aplicación en la degradación de la biomasa, sin embargo, la optimización de las condiciones de cultivo es necesaria para lograr la viabilidad económica.

Influence of volatile fatty acid concentration stability on anaerobic degradation of linear alkylbenzene sulfonate.

Linear alkylbenzene sulfonate (LAS) is an anionic surfactant used in cleaning products, which is usually found in wastewaters. Despite the greater LAS removal rate related to a lower concentrations of volatile fatty acids (VFA), the influence of different ranges of VFA on LAS degradation is not known. LAS degradation was evaluated in upflow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) reactors at different ranges of VFA concentrations. The reactors were fed with a synthetic wastewater containing LAS (14 mg/L). A greater LAS removal rate (40-80%) was related to the lower and narrower range of acetic acid concentration (1-22 mg/L) in the EGSB reactor. In the UASB reactor, the acetic acid concentrations presented a wider range (2-45 mg/L), and some low LAS removal rates (around 20-25%) were observed even at low acetic acid concentrations (<10 mg/L). The high recirculation rate in the EGSB reactor improved substrate-biomass contact, which resulted in a narrower range of VFA and greater LAS removal rate.

The effect of enzymatic pre-hydrolysis of dairy wastewater on the granular and immobilized microbial community in anaerobic bioreactors.

The effect of a lipase-rich enzyme preparation produced by the fungus Penicillium sp. on solid-state fermentation was evaluated in two anaerobic bioreactors (up-flow anaerobic sludge blanket (UASB) and horizontal-flow anaerobic immobilized biomass (HAIB)) treating dairy wastewater with 1200 mg oil and grease/L. The oil and grease hydrolysis step was carried out with 0.1% (w/v) of the solid enzymatic preparation at 30 degrees C for 24 h. This resulted in a final concentration of free acids eight times higher than the initial value. The bioreactors operated at 30 degrees C with hydraulic retention times of 12 h (HAIB) and 20 h (UASB) for a period of 430 days, and had high chemical oxygen demand (COD) removal efficiencies (around 90%) when fed with pre-hydrolyzed wastewater. There was, however, an increase in the effluent oil and grease concentration (from values as low as 17 mg/L to values above 150 mg/L in the UASB bioreactor, and from 38-242 mg/L in the HAIB bioreactor), and oil and grease accumulation in the biomass throughout the operational period (the oil and grease content reached 1.7 times that found in the inoculum of the UASB bioreactor). The HAIB bioreactor gave better results because the support for biomass immobilization acted as a filter, retaining oil and grease at the entry of the bioreactor. The molecular analysis of the Bacteria and Archaea domains revealed significant differences in the microbial profiles in experiments conducted with and without the pre-hydrolysis step. The differences observed in the overall parameters could be related to the microbial diversity of the anaerobic sludge.

Optimization of linear alkylbenzene sulfonate (LAS) degradation in UASB reactors by varying bioavailability of LAS, hydraulic retention time and specific organic load rate.

Degradation of linear alkylbenzene sulfonate (LAS) in UASB reactors was optimized by varying the bioavailability of LAS based on the concentration of biomass in the system (1.3-16 g TS/L), the hydraulic retention time (HRT), which was operated at 6, 35 or 80 h, and the concentration of co-substrates as specific organic loading rates (SOLR) ranging from 0.03-0.18 g COD/g TVS.d. The highest degradation rate of LAS (76%) was related to the lowest SOLR (0.03 g COD/g TVS.d). Variation of the HRT between 6 and 80 h resulted in degradation rates of LAS ranging from 18% to 55%. Variation in the bioavailability of LAS resulted in discrete changes in the degradation rates (ranging from 37-53%). According to the DGGE profiles, the archaeal communities exhibited greater changes than the bacterial communities, especially in biomass samples that were obtained from the phase separator. The parameters that exhibited more influence on LAS degradation were the SOLR followed by the HRT.

Performance and molecular evaluation of an anaerobic system with suspended biomass for treating wastewater with high fat content after enzymatic hydrolysis.

The effect of a lipase-rich fungal enzymatic preparation, produced by a Penicillium sp. during solid-state fermentation, was evaluated in an anaerobic digester treating dairy wastewater with 1200 mg of oil and grease/L. The oil and grease hydrolysis step was carried out with 0.1% (w/v) of solid enzymatic preparation at 30 degrees C for 24 h, and resulted in a final free acid concentration eight times higher than the initial value. The digester operated in sequential batches of 48 h at 30 degrees C for 245 days, and had high chemical oxygen demand (COD) removal efficiencies (around 90%) when fed with pre-hydrolyzed wastewater. However, when the pre-hydrolysis step was removed, the anaerobic digester performed poorly (with an average COD removal of 32%), as the oil and grease accumulated in the biomass and effluent oil and grease concentration increased throughout the operational period. PCR-DGGE analysis of the Bacteria and Archaea domains revealed remarkable differences in the microbial profiles in trials conducted with and without the pre-hydrolysis step, indicating that differences observed in overall parameters were intrinsically related to the microbial diversity of the anaerobic sludge.